Large-Scale Edge Waves Generated by Hurricane Landfall

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Intellectual merit:The hurricane-induced surge and flooding in the coastal areas is an important societal problem. Severe flooding outside the immediate landfall area and a few hours after the landfall can be caused by a freely propagating wave pulse. The cases indeed occurred in the past. The observations of the storm surge induced by Hurricane Wilma landfall on the West Coast of Florida on October 24, 2005 revealed a formation of a wave pulse as Wilma moved inland and the surge was no longer sustained by the wind forcing. The height of the wave pulse exceeded 1.5 m in de-tided sea level data, but it was somewhat obscured in the surge measurements because of its propagating during the low tide. The duration of this wave pulse was ~6 hrs and the propagation speed varied within a range of 10-25 m s-1 indicating an evolution process of the initial disturbance. The wave pulse is identified as an edge wave with large spatial and temporal scales. Such relatively short-lasting waves induced by a hurricane on the continental shelf were not reported before. Most likely, they escaped detection, because a sparse spatial resolution in the standard observational network maintained by NOAA and USGS cannot resolve their phase propagation. Instead, the previous studies were focused on lower-frequency coastally trapped waves (CTW) with periods comparable to or longer than the inertial, which were thought to be prevailing wave modes generated by tropical cyclones. This project will investigate the generation and alongshore evolution of the hurricane-induced edge waves by means of process-oriented numerical modeling. More specifically, the following questions will be addressed: - What are the most favorable conditions for the edge wave generation by a hurricane landfall? The roles of the hurricane size, strength, translation speed and trajectory, as well as the role of shelf topography, will be delineated. - What topographic forms induce the local amplification of the edge waves? The effects of large topographic variations (widening/narrowing shelf, bending coastline, etc.) and smaller features (inlets, estuaries, capes, etc.) will systematically be studied. - What are the mechanisms of the edge wave dissipation? Is the dissipation mostly related with the bottom friction or with the offshore energy radiation? Broader impacts:The results of the project will have applications to national and regional security in such areas as hazard mitigation, disaster prevention, and the development of early warning systems. The results will also be important for coastal zone management and protection, as well as for maritime operations. One graduate student will be supported by this project.